Abstract
The paper presents theoretical background to the occurrence and propagation of imposed thermal load deep inside the structure of airfield pavement. The standard composition of low-shrink cement concrete intended for airfield pavements was presented. The influence of recurring temperature changes on the extent of shrinkage deformations was assessed. The obtained lab test results, combined with observations and analysis of changes of the hardened concrete microstructure, allowed the authors to draw conclusions. It was proven that the suggested concrete mix composition makes it possible to obtain the concrete type of better developed internal microstructure. More micro air voids and reduced distance between the voids were proven, which provides increased frost resistance of concrete. The change of size, structure and quantity of the hydration products in the cement matrix and better developed contact sections resulted in the improvement of the mechanical parameters of hardened concrete. Low-shrink concrete in all analysed cases proved to have increased resistance to the variable environmental conditions. Increased concrete resistance is identified through reduced registered shrinkage deformations and growth of mechanical parameters of concrete. Low-shrink concrete used for airfield structure guarantees extended time of reliable pavement operation.
Highlights
Thermal resistance of the airfield structure is defined as the ability to transfer diversified types of thermal load by pavement layers
On the basis of the analysis of the obtained destructive test results, it was proven that CC-2 series concrete, regardless of the analysed feature, is distinguished by more favourable mechanical parameters (Table 4)
With reference to the airfield pavements, the flexural strength is identified with operational durability of pavement
Summary
Thermal resistance of the airfield structure is defined as the ability to transfer diversified types of thermal load by pavement layers (especially pavement surfacing). Thermal loads of three types are generated onto airfield pavements. The first type includes loads generated as a result of the thermal processes occurring in the hardening concrete mix. The second type includes natural thermal loads occurring in concrete as a result of ambient temperature variations. The factor which causes the occurrence of the imposed thermal loads on the airfield pavements are aircrafts in operation. Placing the engines under the aircraft wings contributes to directing the exhaust gas stream straight onto the pavements. Parameters of exhaust gas stream at nozzle outlet reach the streamflow velocity of 500-600 m/s and gas temperature of 530-900 °C. In the case of turbine jet engines without afterburner, in external channel, the velocity of air stream is 300-400 m/s and its temperature is 30-230 °C [3]
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